How To Understand Battery Capacity

When buying electronic devices such as laptops, notebooks, PDAs, PSPs and cell phones, the first question a consumer asks is, “How long is its battery capacity”? Or probably, “How long are its charging hours?”

These questions stem from the fact that any laptop or computer with a strong hard drive and a good memory, coupled with a battery with a huge capacity, forms a machine with enough power to supply the needs of this fast-paced world. 

Understanding battery capacity begins with understanding its Milli Amp Hours or mAH. This is basically the amount of energy or amperage that is discharged or released from a battery over a period of time until it reaches 100% depth of discharge (DOD), which in layman’s terms means that the battery is empty. Imagine your battery as a fuel tank and the fuel as the battery capacity to better understand this.

For an actual practice of how this is applied, look at the back of your battery and check the number beside the mAH sign. The mAH corresponds to the capacity of the battery. In example, a 9 Volt battery has a mAH of 500. A device that draws 10 ma or milliamperes from this battery will have a battery life of 50 hours. A consumer that knows about these things can then schedule the usage of his/her computer in the most cost efficient way so he/she can take advantage of the current capacity of hard drives out in the market today.

Aside from the amperage, there are other factors that affect battery capacity. The biggest factor is battery life. Each time a battery is recharged after it reaches 100% DOD, battery capacity and battery lifespan decreases. Regularly waiting for a battery to reach 100% DOD before charging will reduce battery capacity and lifespan by as much as 15-20%. This is the reason why the perfect time to charge your battery is when it is 50-80% discharged since there is virtually no change in battery lifespan.

However, it is important to remember that the degradation of battery life is not something that can be stopped. Thus, whether you recharge your battery at 100% or at 50% discharge, its life will still be shortened – the only difference is the speed of its degradation. There is, however, some development in producing other types of batteries that have a much slower rate of degradation, whether at 100 or 50% discharge.

Another key factor in battery capacity is temperature. Battery capacity slightly increases when it is warm, and consequently decreases when it gets cold.

The battery’s physical size is also another factor. The capacity of a battery can measured in the volume and plate area of the actual battery. The larger the plate area, the more it can accommodate.

Two other factors that affect battery capacity are charging and maintenance. Early degradation of battery life is most often caused by overcharging and undercharging. In rare instances, these lead to the destruction of battery plates that makes the batteries unusable. Currently, mineral oil is being looked into as an additive to increase the durability of batteries.

If you have appliances that have large batteries such as electronic scooters or trolling motors, you can charge those using solar panels or inverters to ensure that you don’t undercharge them.

Knowing full well the capacity of your battery can help you in scheduling charging hours or determining if you need to bring extra batteries when traveling. In addition, the knowledge of your battery capacity can help users save in electricity costs and will allow them to enjoy the power of their computer hard drives in the long run.


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